Vacuum processing apparatus

ABSTRACT

This invention relates to a vacuum processing apparatus having vacuum processing chambers the insides of which must be dry cleaned, and to a method of operating such an apparatus. When the vacuum processing chambers are dry-cleaned, dummy substrates are transferred into the vacuum processing chamber by substrates conveyor means from dummy substrate storage means which is disposed in the air atmosphere together with storage means for storing substrates to be processed, and the inside of the vacuum processing chamber is dry-cleaned by generating a plasma. The dummy substrate is returned to the dummy substrate storage means after dry cleaning is completed. Accordingly, any specific mechanism for only the cleaning purpose is not necessary and the construction of the apparatus can be made simple. Furthermore, the dummy substrates used for dry cleaning and the substrates to be processed do not coexist, contamination of the substrates to be processed due to dust and remaining gas can be prevented and the production yield can be high.

This application is a Divisional application of Ser. No. 09/766,587,filed Jan. 23, 2001, which is a Divisional application of applicationSer. No. 09/461,432, filed Dec. 16, 1999,now U.S. Pat. No. 6,330,755which is a Continuation application of application Ser. No. 09/177,495,filed Oct. 23, 1998, now U.S. Pat. No. 6,012,235 which is a Continuationapplication of application Ser. No. 09/061,062, filed Apr. 16, 1998, nowU.S. Pat. No. 5,950,330 which is a Continuation application ofapplication Ser. No. 08/882,731, filed Jun. 26, 1997, now U.S. Pat. No.5,784,799 which is a Divisional application of application Ser. No.08/593,870, filed Jan. 30, 1996, now U.S. Pat. No. 5,661,913 which is aContinuing application of application Ser. No. 08/443,039, filed May 17,1995, now U.S. Pat. No. 5,553,396 which is a Divisional application ofapplication Ser. No. 08/302,443, filed Sep. 9, 1994, now U.S. Pat. No.5,457,896 which is a Continuing application of application Ser. No.08/096,256, filed Jul. 26, 1993, now U.S. Pat. No. 5,349,762 which is aContinuing application of application Ser. No. 07/751,952, filed Aug.29, 1991.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a vacuum processing apparatus and operatingmethod therefor. More specifically, the present invention relates to avacuum processing apparatus having vacuum processing chambers the insideof which must be cleaned, and its operating method.

2. Description of the Prior Art

In a vacuum processing apparatus such as a dry etching apparatus, a CVDapparatus or a sputtering apparatus, a predetermined number ofsubstrates to be treated are stored as one unit (which is generallyreferred to as a “lot”) in a substrate cassette and are loaded in theapparatus. The substrates after being processed are likewise stored inthe same unit in the substrate cassette and are recovered. This is anordinary method of operating these apparatuses to improve theproductivity.

In such a vacuum processing apparatus described above, particularly inan apparatus which utilizes a reaction by an active gas, as typified bya dry etching apparatus and a CVD apparatus, reaction products adhere toand are deposited on a vacuum processing chamber with the progress ofprocessing. For this reason, problems such as degradation of vacuumperformance, the increase of dust, the drop of the levels of opticalmonitoring signals occur. To solve these problems, conventionally theinsides of the vacuum processing chambers are cleaned periodically.Cleaning operations include so-called “wet cleaning” which is wiping-offof the adhering matters by use of an organic solvent, etc., andso-called “dry cleaning” in which an active gas or plasma is used fordecomposing adhering matters. Dry cleaning is superior from the aspectof the working factor and efficiency. These features of the dry cleaninghave become essential with the progress in automation of productionlines.

An example of vacuum processing apparatuses having such a dry cleaningfunction is disclosed in Japanese Utility Model Laid-Open No.127125/1988. This apparatus includes a preliminary vacuum chamber forintroducing wafers to be treated into a processing chamber from anatmospheric side to a vacuum side, which is disposed adjacent to theprocessing chamber through a gate valve, dummy wafers are loaded in thepreliminary vacuum chamber and are transferred into the processingchamber by exclusive conveyor means before the processing chamber issubjected to dry cleaning, and the dummy wafer is returned to the vacuumpreparatory chamber by the conveyor means after dry cleaning iscompleted.

SUMMARY OF THE INVENTION

In the prior art technology described above, the structure of the vacuumprocessing apparatus is not much considered. The preliminary vacuumchamber for storing the dummy wafers must have a large capacity, theexclusive conveyor means is necessary for transferring the dummy wafersand thus, the apparatus is complicated in structure.

Dummy wafers used for plasma cleaning are again returned to thepreliminary vacuum chamber and are made to stand by. In this instance,reaction products generated during plasma cleaning and residual gas usedfor plasma cleaning adhere on the used dummy wafers. Thereafter, normalprocessing for wafers is resumed.

Therefore, the used dummy wafers and unprocessed wafers exist in mixtureinside the preliminary vacuum chamber and this state is not desirablefrom the aspect of contamination of unprocessed wafers.

The present invention provides a vacuum processing apparatus whichsolves the problems described above, is simple in structure, preventscontamination of unprocessed substrates and accomplishes a highproduction yield. A vacuum processing apparatus having vacuum processingchambers the insides of which are dry-cleaned after substrates to betreated are processed in vacuum is provided with first storage means forstoring substrates to be treated, second storage means for storing dummysubstrates, the first and second storage means being disposed in theair, conveyor means for transferring the substrates to be processedbetween the first storage means and the vacuum processing chambers andfor transferring the dummy substrates between the second storage meansand the vacuum processing chambers, and control means for controllingthe conveyor means so as to transfer the dummy substrates between thesecond storage means and the vacuum processing chambers before and afterdry cleaning of the vacuum processing chambers. A method of operating avacuum processing apparatus having vacuum processing chambers theinsides of which are dry-cleaned after substrates to be processed areprocessed in vacuum comprises the steps of disposing first storage meansfor storing the substrates to be processed together with second storagemeans for storing dummy substrates in the air atmosphere, transferringthe substrates to be processed between the first storage means and thevacuum processing chambers and vacuum-processing the substrates to beprocessed, and transferring the dummy substrates between the secondstorage means and the vacuum processing chambers before and afterdry-cleaning of the vacuum processing chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a dry etching apparatus as an embodiment of avacuum processing apparatus in accordance with the present invention;and

FIG. 2 is a vertical sectional view taken along line 1—1 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As substrates to be processed are processed in a vacuum processingapparatus, reaction products adhere to and are deposited in vacuumprocessing chambers. The reaction products adhering to and deposited inthe vacuum processing chambers are removed by disposing dummy wafersinside the vacuum processing chambers and by conducting dry-cleaning. Tocarry out dry cleaning, the timings of dry cleaning of the vacuumprocessing chambers are determined and during or after the processing ofa predetermined number of substrates to be processed, dummy substratesare conveyed by substrate conveyor means from dummy substrate storagemeans disposed in the air atmosphere together with processed substratestorage means, and are then disposed inside the vacuum processingchambers. After the dummy substrates are thus disposed, a plasma isgenerated inside each of the vacuum processing chambers to executedry-cleaning inside the vacuum processing chamber. After dry-cleaninginside the vacuum processing chambers is completed, the dummy substratesare returned from the vacuum processing chambers to the dummy substratestorage means by the substrate conveyor means. In this manner, apreliminary vacuum chamber and an exclusive transfer mechanism bothnecessary in prior art techniques become unnecessary, and the apparatusstructure gets simplified. The dummy substrates used for thedry-cleaning and the substrates to be processed do not co-exist insidethe same chamber, so that contamination of substrates to be processeddue to dust and remaining gas is prevented and a high production yieldcan be achieved.

Hereinafter, an embodiment of the present invention will be explainedwith reference to FIGS. 1 and 2.

FIGS. 1 and 2 show a vacuum processing apparatus of the presentinvention which is, in this case, a dry-etching apparatus for etchingwafers, i.e., substrates to be processed by plasma.

Cassette tables 2 a to 2 c are disposed in an L-shape in this case inpositions such that they can be loaded into and unloaded from theapparatus without changing their positions and postures. In other words,the cassettes 1 a to 1 c are fixed always in predetermined positions ona substantially horizontal plane, while the cassette tables 2 a and 2 bare disposed adjacent to and in parallel with each other on one of thesides of the L-shape. The cassette table 2 c is disposed on the otherside of the L-shape. The cassettes 1 a and 1 b are for storingunprocessed wafers and for recovering the processed wafers. They canstore a plurality (usually 25) of wafers 20 as the substrates to betreated. The cassette 1 c in this case is for storing the dummy wafersfor effecting dry-cleaning using plasma (hereinafter referred to as“plasma-cleaning”) and recovering the dummy wafers afterplasma-cleaning. It can store a plurality of (usually twenty-fivepieces) dummy wafers 30.

A load lock chamber 5 and unload lock chamber 6 are so disposed as toface the cassette tables 2 aand 2 b, and a conveyor 13 is disposedbetween the cassette tables 2 a, 2 b and the load lock chamber 5 and theunload lock chamber 6. The load lock chamber 5 is equipped with anevacuating device 3 and a gas introduction device 4, and can loadunprocessed wafers in the vacuum apparatus through a gate valve 12 a.The unload lock chamber 6 is similarly equipped with the evacuatingdevice 3 and the gas introduction device 4, and can take out processedwafers to the atmosphere through a gate valve 12 d. The conveyor 13 isequipped with a robot having X, Y, Z and ÷ axes, which operates so as todeliver and receive the wafers 20 between the cassettes 1 a, 1 b and theload lock and unload lock chambers 5 and 6 and the dummy wafers 30between the cassette 1 c and the load lock and unload lock chambers 5and 6.

The load lock chamber 5 and the unload lock chamber 6 are connected to atransfer chamber 16 through the gate valves 12 b and 12 c. The transferchamber 16 is rectangular, in this case, and etching chambers 11 a, 11 band 11 c are disposed on the three side walls of the transfer chamber 16through gate valves 15 a, 15 b and 15 c, respectively. A conveyor 14capable of delivering the wafers 20 or the dummy wafers 30 from the loadlock chamber 5 to the etching chambers 11 a, 11 b, 11 c and ofdelivering them from the chambers 11 a, 11 b, 11 c to the unload lockchamber 6 is disposed inside the transfer chamber 16. The transferchamber 16 is equipped with an evacuating device 17 capable ofindependent evacuation.

The etching chambers 11 a, 11 b, 11 c have the same structure and canmake the same processing. The explanation will be given on the etchingchamber 11 b by way of example. The etching chamber 11 b has a sampletable 8 b for placing the wafers 20 thereon, and a discharge chamber isso provided as to define a discharge portion 7 b above the sample table8 b. The etching chamber 11 b includes a gas introduction device 10 bfor introducing a processing gas in the discharge portion 7 b and anevacuating device 9 b for decreasing the internal pressure of theetching chamber 11 b to a predetermined pressure. The etching chamber 11b further includes generation means for generating a microwave and amagnetic field for converting processing gas in the discharge portion 7b to the plasma.

A sensor 18 for measuring the intensity of plasma light is disposed atan upper part of the etching chamber. The measured value of the sensor13 is inputted to a controller 19. The controller 19 compares themeasured value from the sensor 18 with a predetermined one anddetermines the timing of cleaning inside the etching chamber. Thecontroller 19 controls the conveyors 13 and 14 to control the transferof the dummy wafers 30 between the cassette 1 c and the etching chambers11 a to 11 c.

In a vacuum processing apparatus having the construction describedabove, the cassettes 1 a, 1 b storing unprocessed wafers are firstplaced onto the cassette tables 2 a, 2 b by a line transfer robot whichoperates on the basis of the data sent from a host control apparatus, orby an operator. On the other hand, the cassette 1 c storing the dummywafers is placed on the cassette table 2 c. The vacuum processingapparatus executes the wafer processing or plasma cleaning on the basisof recognition by itself of the production data provided on thecassettes 1 ato 1 c, of the data sent from the host control apparatus,or of the command inputted by an operator.

For instance, the wafers 20 are sequentially loaded in the order fromabove into the etching chambers 11 a, 11 b, 11 c by the conveyors 13 and14, and are etched. The etched wafers are stored in their originalpositions inside the cassette 1 aby the conveyors 14 and 13. In thiscase, from the start to the end of the operation, without changing theposition and posture of the cassettes, the unprocessed wafers are takenout from the cassettes and are returned in their original positionswhere the wafers have been stored, and are stored there. In this manner,the apparatus can easily cope with automation of the production line,contamination of the wafers due to dust can be reduced and highproduction efficiency and high production yield can thus beaccomplished.

As etching is repeated, the reaction products adhere to and aredeposited on the inner wall of the etching chambers 11 a to 11 c.Therefore, the original state must be recovered by removing the adheringmatters by plasma cleaning. The controller 19 judges the timing of thisplasma cleaning. In this case, a portion through which the plasma lightpasses is provided in each of the etching chambers 11 a to 11 c. Thesensor 18 measures the intensity of the plasma light passing throughthis portion and when the measured value reaches a predetermined one,the start timing of plasma cleaning is judged. Alternatively, the timingof plasma cleaning may be judged by counting the number of wafersprocessed in each etching chamber by the controller 19 and judging thetiming when this value reaches a predetermined value. The actual timingof plasma cleaning that is carried out may be during a processing of apredetermined number of wafers in the cassette 1 a or 1 b, after theprocessing of all the wafers 20 in a cassette is completed and beforethe processing of wafers in the next cassette.

Plasma cleaning is carried out in the following sequence. In this case,the explanation will be given about a case where the etching chambers 11a to 11 c are subjected to plasma cleaning by using three dummy wafers30 among the dummy wafers 30 (twenty-five dummy wafers are stored inthis case) stored in the cassette 1 c.

Dummy wafers 30 which are stored in the cassette 1 c and are not usedyet or can be used because the number of times of use for plasmacleaning is below a predetermined one are drawn by the conveyor 13. Atthis time, dummy wafers 30 stored in any position in the cassette 1 cmay be used but in this case, the position numbers of the dummy wafersin the cassette and their number of times of use are stored in thecontroller 19, and accordingly dummy wafers having smaller numbers oftimes of use are drawn preferentially. Then, the dummy wafers 30 areloaded in the load lock chamber 5 disposed on the opposite side to thecassette 1 a by the conveyor 13 through the gate valve 12 a in the sameway as the transfer at the time of etching of wafers 20. After the gatevalve 12 a is closed, the load lock chamber 5 is evacuated to apredetermined pressure by the vacuum exhaust device 3 and then the gatevalves 12 b and 15 a are opened. The dummy wafers 30 are transferred bythe conveyor 14 from the load lock chamber 5 to the etching chamber 11 athrough the transfer chamber 16 and are placed on the sample table 8 a.After the gate valve 15 a is closed, plasma cleaning is carried out inthe etching chamber 11 a in which the dummy wafers 30 are disposed,under a predetermined condition.

In the interim, the gate valves 12 a, 12 b are closed and the pressureof the load lock chamber 5 is returned to the atmospheric pressure bythe gas introduction device 4. Next, the gate valve 12 a is opened andthe second dummy wafer 30 is loaded in the load lock chamber 5 by theconveyor 13 in the same way as the first dummy wafer 30, and evacuationis effected again by the evacuating device 3 to a predetermined pressureafter closing the gate valve 12 a. Thereafter, the gate valves 12 b and15 b are opened and the second dummy wafer 30 is transferred from theload lock chamber 5 to the etching chamber 11 b through the transferchamber 16 by the conveyor 14. Plasma cleaning is started after the gatevalve 15 b is closed.

In the interim, the third dummy wafer 30 is transferred into the etchingchamber 11 c in the same way as the second dummy wafer 30 and plasmacleaning is carried out.

After plasma cleaning is completed in the etching chamber 11 a in whichthe first dummy wafer 20 is placed, the gate valves 15 a and 12 c areopened. The used dummy wafer 30 is transferred from the etching chamber11 a to the unload lock chamber 6 by the conveyor 14. Then, the gatevalve 12 c is closed. After the pressure of the unload lock chamber 6 isreturned to the atmospheric pressure by the gas introduction device 4,the gate valve 12 d is opened. The used dummy wafer 30 transferred tothe unload lock chamber 6 is taken out in the air by the conveyor 13through the gate valve 12 d and is returned to its original position inthe cassette 1 c in which it is stored at the start.

When plasma cleaning of the etching chambers 11 b and 11 c is completed,the second and third dummy wafers 20 are returned to their originalpositions in the cassette 1 c.

In this way, the used dummy wafers 30 are returned to their originalpositions in the cassette 1 c and the dummy wafers 30 are always stockedin the cassette 1 c. When all the dummy wafers 30 in the cassette 1 care used for plasma cleaning or when the numbers of times of use of thewafers 30 reach the predetermined ones after the repetition of use, thedummy wafers 30 are replaced as a whole together with the cassette 1 c.The timing of this replacement of the cassette is managed by thecontroller 19 and the replacement is instructed to the host controlapparatus for controlling the line transfer robot or to the operator.

Although the explanation given above deals with the case where theetching chambers 11 a to 11 c are continuously plasma-cleaned by the useof three dummy wafers 30 among the dummy wafers 30 in the cassette 1 c,other processing methods may be employed, as well.

For example, the etching chambers 11 a to 11 c are sequentiallyplasma-cleaned by the use of one dummy wafer 30. In the case of suchplasma cleaning, unprocessed wafers 20 can be etched in etching chambersother than the one subjected to plasma cleaning, and plasma cleaning canthus be carried out without interrupting etching.

If the processing chambers are different, for example, there are anetching chamber, a post-processing chamber and a film-formation chamber,and wafers are sequentially processed while passing through each ofthese processing chambers, each of the processing chambers can besubjected appropriately to plasma cleaning by sending dummy wafers 30during the processing of the wafers 20 which are stored in the cassette1 a or 2 a and drawn and sent sequentially, by passing merely the dummywafers 30 through the processing chambers for which plasma cleaning isnot necessary, and by executing plasma cleaning only when the dummywafers 30 reach the processing chambers which need plasma cleaning.

According to the embodiment described above, the cassette storing thedummy wafers and the cassettes storing the wafers to be processed aredisposed together in the air, the dummy wafers are loaded from thecassette into the apparatus by the same conveyor as the conveyor fortransferring the wafers, at the time of cleaning and the used dummywafers are returned to their original positions in the cassette. In thisway, a mechanism for conducting exclusively plasma cleaning need not beprovided, and the construction of the apparatus can be simplified. It isnot necessary to handle plasma cleaning as a particular processingsequence, but the plasma cleaning can be incorporated in an ordinaryetching processing and can be carried out efficiently in a series ofoperations.

The dummy wafers used for plasma cleaning are returned to their originalpositions in the cassette placed in the air. Accordingly, the used dummywafers and the wafers before and after processing do not exist mixedlyin the vacuum chamber, so that contamination of wafers due to dust andremaining gas does not occur unlike conventional apparatuses.

The used dummy wafers are returned to their original positions in thecassette and the numbers of times of their use is managed. Accordingly,it is possible to prevent the confusion of the used dummy wafers withthe unused dummy wafers and the confusion of the dummy wafers havingsmall numbers of times of use with the dummy wafers having large numbersof times of use. For these reasons, the dummy wafers can be usedeffectively without problem when plasma cleaning is carried out.

Furthermore, in accordance with the present invention, the apparatus canhave a plurality of processing chambers and can transfer wafers anddummy wafers by the same conveyor. Since plasma cleaning can be carriedout by managing the timing of cleaning of each processing chamber by thecontroller, the cleaning cycle can be set arbitrarily, dry cleaning canbe carried out without interrupting the flow of the processing, theprocessing can be efficiently made and the productivity can be improved.

As described above, according to the present invention, there areeffects that the construction of the apparatus is simple, the substratesto be processed are free from contamination and the production yield ishigh.

What is claimed is:
 1. A vacuum processing system, comprising: a firstconveyor structure for transferring a cassette; a cassette mount unitfor holding the cassette; a second conveyor structure for transferring awafer from the cassette held on the cassette mount unit; a vacuum loaderprovided with a third conveyor structure and a vacuum processingchamber; and at least one lock chamber disposed between the secondconveyor structure and the third conveyor structure, wherein: the firstconveyor structure, the second conveyor structure and the third conveyorstructure are respective provided with a first robot, a second robot anda third robot, the second conveyor structure is disposed between thecassette mount unit and the at least one lock chamber, and the thirdrobot is disposed in a conveyor chamber of the vacuum loader and facesto the at least one lock chamber, and the second robot is positioned toface to a cassette, held on the cassette mount unit, for holding a setof wafers, and the second robot is adapted to transfer the wafers one byone to the at least one lock chamber, with a wafer being disposed in arespective lock chamber, and the third robot is disposed in the conveyorchamber of the vacuum loader so as to face the at least one lockchamber.
 2. The vacuum processing system according to claim 1, whereineach of the first, second and third robots has an arm which moveshorizontally and rotationally.
 3. The vacuum processing system accordingto claim 2, wherein each of the first and second robots can move in upand down directions.
 4. The vacuum processing system according to claim3, wherein the first robot transfers a cassette, and the second andthird robots transfer respectively a wafer.
 5. The vacuum processingsystem according to claim 4, further comprising a computer controlsystem for controlling movement of the first, second and third robots.6. The vacuum processing system according to claim 4, wherein the firstrobot and the second robot are exposed to the air, and the third robotis disposed in a vacuum condition.
 7. The vacuum processing systemaccording to claim 1, wherein the first conveyor structure and thesecond conveyor structure respectively include tracks in parallel toeach other.
 8. The vacuum processing system according to claim 1,wherein a set of two cassettes is disposed on the cassette mount unit,and the first robot is movable along a front surface of the set of twocassettes.
 9. The vacuum processing system according to claim 1, whereinthe first conveyor structure is movable along a front surface of thecassette mount unit, parallel thereto.
 10. A vacuum processing system,comprising: a first conveyor structure for transferring a cassette; acassette mount unit for holding the cassette; a second conveyorstructure for transferring a wafer from the cassette held on thecassette mount unit; a vacuum loader provided with a third conveyorstructure and at least one vacuum processing chamber; and at least onelock chamber disposed between the second conveyor structure and thethird conveyor structure; wherein: the first conveyor structure, thesecond conveyor structure and third conveyor structure are respectivelyprovided with a first robot, a second robot and a third robot, and thesecond conveyor structure and the third conveyor structure are disposedin a direction perpendicular to a traveling direction of the firstconveyor structure, and the second robot is positioned to face acassette, on the cassette mount unit, for holding a set of wafers, andthe second robot is adapted to transfer the wafers one by one to the atleast one lock chamber, the at least one lock chamber being providedwith both an inlet and an outlet located in a horizontal line, and thethird robot is disposed in a conveyor chamber of the vacuum loader so asto be located in the horizontal line.
 11. The vacuum processing systemaccording to claim 10, wherein the second robot is adapted to transfer awafer from the cassette mount unit to a lock chamber, of the at leastone lock chamber, and the third robot is adapted to transfer the waferfrom the lock chamber to the conveyor chamber of the vacuum loader. 12.The vacuum processing system according to claim 11, wherein the thirdrobot is adapted to transfer a processed wafer from the conveyor chamberto a lock chamber, of the at least one lock chamber, and the secondrobot is adapted to transfer the processed wafer from the lock chambercontaining the processed wafer to the cassette mount unit.
 13. Thevacuum processing system according to claim 12, wherein the first robotis adapted to transfer a cassette holding the processed wafer from thecassette mount unit to the first conveyor structure.
 14. The vacuumprocessing system according to claim 10, wherein the first robot, thesecond robot and the third robot are adapted to maintain a plane of asurface of a wafer substantially horizontal during transferring thewafer, so that the plane of the surface of the wafer is kept in ahorizontal state at steps from the first conveyor structure to thevacuum processing chamber.
 15. The vacuum processing system according toclaim 14, wherein the second robot travels on a track and is moved in upand down directions.
 16. The vacuum processing system according to claim10, wherein the at least one lock chamber comprises a load lock chamberand an unload lock chamber which are separate chambers.
 17. The vacuumprocessing system according to claim 16, wherein the second robot isadapted to transfer a wafer to the load lock chamber from the firstconveyor structure and is adapted to transfer out a processed wafer fromthe unload lock chamber to the first conveyor structure.
 18. The vacuumprocessing system according to claim 10, wherein the second robot andthe third robot form a sole route for a wafer and a processed waferwhich are transferred.
 19. The vacuum processing system according toclaim 10, wherein a wafer is exposed to the air at the stages of thefirst conveyor structure, the cassette mount unit and the secondconveyor structure.
 20. The vacuum processing system according to claim10, wherein the cassette mount unit is provided with an open structurefor taking in a cassette, and a cassette on the cassette mount unit isprovided with a window portion open to the second conveyor structure.21. The vacuum processing system according to claim 10, wherein thesecond robot is a sole robot which travels on a track for transferring awafer between the cassette mount unit and the second conveyor structure.22. The vacuum processing system according to claim 21, wherein the atleast one lock chamber is provided with a load lock chamber and anunload lock chamber, and the second robot transfers the wafer betweenthe second conveyor structure and the load lock chamber, and a processedwafer between the unload lock chamber and the second conveyor structure.23. The vacuum processing system according to claim 21, furthercomprising a control device which controls movement of the three robots,and the second robot takes a processed wafer to a same cassette fromwhich the wafer had been taken out for a process treatment.
 24. Thevacuum processing system according to claim 10, wherein while the secondrobot is transferring a wafer from the cassette mount unit to the secondconveyor structure, the third robot is transferring a wafer from a lockchamber to the vacuum loader.
 25. The vacuum processing system accordingto claim 10, wherein while the second robot is transferring a wafer fromthe cassette mount unit to the second conveyor structure, the thirdrobot is transferring a wafer from the conveyor chamber to a vacuumprocessing chamber.
 26. The vacuum processing system according to claim10, wherein while the second robot is transferring a wafer from thecassette mount unit to the second conveyor structure, the third robot istransferring a processed wafer from a vacuum processing chamber to theconveyor chamber.
 27. The vacuum processing system according to claim10, wherein while the second robot is transferring a wafer from thecassette mount unit to the second conveyor structure, the third robot istransferring a processed wafer from the conveyor chamber to a lockchamber.
 28. The vacuum processing system according to claim 10, whereinwhile the second robot is transferring a wafer from the second conveyorstructure to a lock chamber, the third robot is transferring a waferfrom the conveyor chamber to a vacuum processing chamber.
 29. The vacuumprocessing system according to claim 10, wherein while the second robotis transferring a wafer from the second conveyor structure to a lockchamber, the third robot is transferring a processed wafer from a vacuumprocessing chamber to the conveyor chamber.
 30. The vacuum processingsystem according to claim 10, wherein while the third robot istransferring a processed wafer from the conveyor chamber to a lockchamber, the second robot is transferring a processed wafer from thesecond conveyor structure to the cassette mount unit.
 31. The vacuumprocessing system according to claim 10, wherein the vacuum loaderincludes plural vacuum processing chambers, and the third robot is asole robot which accesses to the plural vacuum processing chambers. 32.The vacuum processing system according to claim 10, wherein the at leastone lock chamber includes a load lock chamber and an unload lock chamberwhich are separate from each other, and the third robot is a sole robotwhich accesses both the load lock chamber and the unload lock chamber.33. The vacuum processing system according to claim 32, wherein thevacuum loader includes plural vacuum processing chambers, and the solerobot accesses to the plural vacuum processing chambers.